Neutron diffraction study of the irreversible R-M-A-M-C phase transition in single crystal Pb[(Zn1/3Nb2/3)(1-x)Ti-x]O-3

Single crystals of the relaxor PZN-xPT display an enormously strong piezoel ectric character. Recent x-ray scattering studies have revealed novel elect ric-field induced phase transitions in PZN-8%PT. As-grown crystals exhibit a rhombohedral structure that, under application of an electric field orien ted along [001]. transforms into a monoclinic (M-A) phase, and then irrever sibly to another monoclinic (M-C) phase with increasing field strength. Sin ce the latter phase change is very unusual, its transition sequence hats be en investigated by using triple-axis neutron scattering techniques so that the "skin effect" observed by x-ray scattering can be avoided, and the enti re crystal bulk is probed. Contour maps of the elastic scattering have been mapped out in each phase in the (H0L) zone with high q-resolution. Increas ing the field strength within the Me phase induces a sharp c-axis jump arou nd 15 kV/cm. This jump was observed easily with x-rays in previous studies, but it was not observed in 5 different crystals examined with neutrons. A subsequent high-energy x-ray study of the same crystals showed that the c-a -xis jump is distributed within the crystal volume, thereby washing out the jump. The observed R-M-A-M-C transformational path is in perfect accord wi th very recent first principles calculations by Bellaiche, Garcia, and Vand erbilt in the PZT system.